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Temporal range: 19–0 Ma Burdigalian, Early Miocene – Recent
Acanthognathus ocellatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acanthognathus
Mayr, 1887
Type species
Acanthognathus ocellatus
7 species
1 fossil species
(Species Checklist, Species by Country)


Acanthognathus ocellatus


Specimen Label

Evolutionary Relationships

Ochetomyrmex (2 species), Tranopelta (2 species)

Allomerus (8 species), Blepharidatta (4 species), Diaphoromyrma (1 species), Lachnomyrmex (16 species), Wasmannia (11 species)

  (7 species)

  (2 species)

  (7 species)

  (4 species)

  (29 species)

  (16 species)

  (19 species)

  (9 species)

Acromyrmex (55 species), Apterostigma (44 species), Atta (20 species), Cyatta (1 species), Cyphomyrmex (23 species), Kalathomyrmex (1 species), Mycetophylax (21 species), Mycetagroicus (4 species), Mycetarotes (4 species), Mycetosoritis (2 species), Mycocepurus (6 species), Myrmicocrypta (31 species), Sericomyrmex (11 species), Trachymyrmex (9 species), Xerolitor (1 species)

Basiceros (8 species), Cephalotes (119 species), Eurhopalothrix (53 species), Octostruma (34 species), Phalacromyrmex (1 species), Pheidole (1,292 species), Pilotrochus (1 species), Procryptocerus (44 species), Protalaridris (7 species), Rhopalothrix (16 species), Strumigenys (852 species), Talaridris (1 species)

Based on Ward et al. (2014), Blaimer et al. (2018) and Li et al. (2018).

Species in this Central and South American genus are found in rotten logs, hollow twigs and branches and sections of wood buried in leaf litter. Colony size is rather small, often less than 20 workers. Individual foragers can be seen hunting collembola prey with mandibles wide open on the surface of leaf litter.

At a Glance • Trap-Jaw  



Mandibles linear and elongate, their bases extremely closely approximated and with kinetic mode of action, each with an apical fork of 3 spiniform teeth that interlock at full closure. Preapical dentition sometimes present but often absent. Mandibles at full gape open to 170 degrees or more. Basal process of mandible a long curved spur that is minutely bifurcated apically; when mandibles fully closed the basal processes cross over and are ventral to the labrum and at the apex of the labio-maxillary complex; when fully open the mandibles are braced in that position by opposition of the basal processes alone. Trigger hairs arise from the mandibles (one from each); trigger hairs lie flat against margin when mandible closed, becoming erect as mandibles open. Palp formula 0,1. Labrum extremely reduced to vestigial, represented by a narrow Y-shaped sclerite; labrum not taking part in mandibular locking mechanism. Buccal cavity narrow, parallel-sided anteriorly; labio-maxillary complex narrow.

AntWeb icon 02.png See images of species within this genus

Keys including this Genus


Keys to Species in this Genus


The seven species in this genus are found in Central and South America. The single extinct species is Miocene age from Dominican Republic amber.

Distribution and Richness based on AntMaps


Fossils are known from: Dominican amber, Dominican Republic (Burdigalian, Early Miocene).


Ants of the genus Acanthognathus stalk small insects and catch their prey by a strike with their long, thin mandibles. The mandibles close in less than 2.5 ms and this movement is controlled by a specialized closer muscle. In Acanthognathus, unlike other insects, the mandible closer muscle is subdivided into two distinct parts: as in a catapult, a large slow closer muscle contracts in advance and provides the power for the strike while the mandibles are locked open. When the prey touches specialized trigger hairs, a small fast closer muscle rapidly unlocks the mandibles and thus releases the strike. The fast movement is steadied by large specialized surfaces in the mandible joint and the sensory-motor reflex is controlled by neurons with particularly large, and thus fast-conducting, axons.


Worker Morphology

  • Antennal segment count: 11
  • Antennal club: 2
  • Palp formula: 0,1
  • Total dental count: 3-8
  • Spur formula: 0, 0
  • Eyes: present
  • Scrobes: absent
  • Sting: present


The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • ACANTHOGNATHUS [Myrmicinae: Dacetini]
    • Acanthognathus Mayr, 1887: 578. Type-species: Acanthognathus ocellatus, by monotypy.

Baroni Urbani & De Andrade (2007) - Synapomorphies resulting from our analysis:

Worker (and gyne) metapleural gland very close to propodeal spiracle. CI 0.62, RI 0.40. This trait appears also in Epopostruma, Microdaceton, Protalaridris, a. o. as coded also by BOLTON (1999, Table 1) for his Dacetonini.

Worker (and gyne) scape straight at base. CI 0.50, RI 0.33. The straight condition of Acanthognathus is shared with Daceton.

Worker (and gyne) antennae 11-jointed. CI 0.20, RI 0.50 for the 11-12 jointed state.

This list, however, does not evidentiate the main synapomorphy for the species of the genus, i.e. our char. #13, state 2, the basimandibular process long and apically bifurcated. The reason for this omission is a purely logical pitfall: since state #2 appears only in Acanthognathus and state #1 is present in all the other genera of the clade, it is impossible to ascertain whether the ancestor of the whole clade presented state #1 or #2 and hence if #2 is exclusive of Acanthognathus or common to Acanthognathus and the hypothetical ancestor of the whole clade.

See also

  • Dalla Torre, 1893: 148 (catalogue)
  • Emery, 1924d: 317 (diagnosis, catalogue)
  • Smith, M.R. 1944c: 150 (all species key)
  • Brown & Kempf, 1969: 89 (diagnosis, all species revision, key)
  • Kempf, 1972a: 9 (catalogue)
  • Bolton, 1994: 106 (synoptic classification)
  • Bolton, 1995a: 1047 (census)
  • Bolton, 1995b: 53 (catalogue)
  • Gronenberg, Brandão, et al. 1998: 227 (mandible mechanism)
  • Bolton, 1999: 1650 (diagnosis, review of genus, phylogeny)
  • Bolton, 2000: 15 (diagnosis, species synopsis)
  • Galvis & Fernández, 2009: 247 (all species key)